Improvements
1) Periodic boundary conditions for cubic box
2) 



Bugs
1) Spherical -- check the values of multipole and local coefficients.
   use :  utestSphericalDirectDebug.cpp 
2) Intel compiler : need -fp-model precise -fp-model source -fimf-precision=low for Spherical (?????)


ToDO
1) Change the algorithm for periodic boundary conditions. (Ewald approach)
2) Non cubic box.
3) Compute the virial for MD simulations
4) Hybrid parallelism for the tree build
5) Use the same parameters for all tests (-f -file -h -depth ...)